The present invention relates to a chemically amplified resist material for use in fabrication process or the like for semiconductor devices, a topcoat film material for use in forming a topcoat film on a resist film and a pattern formation method using them.
In accordance with the increased degree of integration of semiconductor integrated circuits and downsizing of semiconductor devices, there are increasing demands for further rapid development of lithography technique. Currently, pattern formation is carried out through photolithography using exposing light of a mercury lamp, KrF excimer laser, ArF excimer laser or the like. Moreover, attempts are recently being made to apply immersion lithography to an ArF light source. Under these circumstances, it is regarded significant to elongate the lifetime of ArF excimer laser lithography beyond a 65-nm node generation, and resist materials to be used for this purpose are now under development.
With respect to a resist material for an ArF light source, it is reported that the resolution of a pattern to be formed is improved by changing the composition of a polymer included in the resist material as a principal component (see, for example, S. W. Yoon et al., “Influence of resin properties to resist performance at ArF lithography”, Proc. SPIE, vol. 5376, p. 583 (2004)).
Now, a conventional pattern formation method using a chemically amplified resist material will be described with reference to FIGS. 9A through 9D.
First, a positive chemically amplified resist material having the following composition is prepared:
Base polymer: poly((2-methyl-2-adamantyl methacrylate)2g(50 mol %) - (γ-butyrolactone methacrylate) (40 mol%) - (2-hydroxyadamantyl methacrylate) (10 mol %))Photo-acid generator: triphenylsulfonium nonafluorobutane0.06gsulfonateQuencher: triethanolamine0.001gSolvent: propylene glycol monomethyl ether acetate20g
Next, as shown in FIG. 9A, the aforementioned chemically amplified resist material is applied on a substrate 1 and the resultant substrate is annealed with a hot plate at a temperature of 90° C. for 60 seconds, so as to form a resist film 2 with a thickness of 0.35 μm.
Then, as shown in FIG. 9B, pattern exposure is carried out by irradiating the resist film 2 with exposing light 4 of ArF excimer laser having NA (numerical aperture) of 0.85 through a mask 3.
After the pattern exposure, as shown in FIG. 9C, the resist film 2 is baked with a hot plate at a temperature of 110° C. for 60 seconds.
Thereafter, the resultant resist film 2 is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern 2a made of an unexposed portion of the resist film 2 and having a line width of 0.065 μm is formed as shown in FIG. 9D.
As shown in FIG. 9D, however, the resolution and the shape of the pattern cannot be improved at all by the conventional method in which the composition of the polymer is merely changed.
When the resist pattern 2a in such a defective shape is used for etching a target film, the resultant pattern of the target film is also in a defective shape, which disadvantageously lowers the productivity and the yield in the fabrication process for semiconductor devices.